1. Field of the Invention
The present invention relates to an apparatus for producing electrolyzed water for separating liquid such as water (which will be referred to as subject water to be electrolyzed, or simply subject water hereinafter) by electrolysis into electrolyzed acidic water and electrolyzed alkaline water, or for merely electrolyzing liquid such as water to produce electrolyzed water.
2. Description of the Related Art
The apparatus for producing electrolyzed acidic water and electrolyzed alkaline water are shown, for example, in U.S. Pat. Nos. 5,055,170 and 5,234,563.
In the apparatus for producing electrolyzed water of this type, the subject water to be electrolyzed such as city water is supplied into the electrolytic cell, and DC current is supplied to between anode and cathode plates. Then, an electrolysis of the water is carried out in the electrolytic cell and as a result, the concentration of hydrogen ion is increased in an area adjacent the anode plate to provide electrolyzed acidic water, while the concentration of hydroxide ion is increased in an area adjacent the cathode plate to provide alkaline water.
In this case, factors governing the pH (potential of Hydrogen) value of the electrolyzed water produced by electrolysis are the flow rate (by volume) of subject water which flows through the electrolytic cell, the current density across the electrode plates and the time of contact of the subject water with the electrode plates. In other words, the pH value of the electrolyzed water, the flow rate and the sizes of components of the electrolyzed water producer(such as the electrolytic cell, the electrode plates and a power source) are influenced by one another.
For this reason, when the amount of electrolyzed water discharged per unit time is intended to be increased while maintaining a desired pH value, it is necessary to supply a large amount of electric power to the subject water, and it is a conventional practice to increase the size of the power source, or to increase the area of the electrode plate, or to provide a large number of electrode plates.
However, for example, when the electrolyzed water is put into use as drinking water or for disinfection or sterilization, or into a domestic use, a business use or an industrial use, the conditions demanded such as the pH value, the discharge amount per unit time and the like are diverse dependent upon the application of the electrolyzed water producer and hence, in the prior art electrolyzed water producer, components such as the electrolytic cell, the electrode plates, the power source and the like must be designed and produced at each time in a specification meeting the demand.
For this reason, a lot of time is required for designing each component, and huge costs are required for equipments such as a mold for producing each component, a fabricating equipment and the like. In addition, the number of exclusively used components is increased and hence, even during assembling, the management for the components is troublesome. As a result, it is difficult to timely provide apparatus for producing electrolyzed water and to realize a reduction in cost. Particularly, notwithstanding that super electrolyzed water such as super acidic water is extremely excellent in a social contribution for a medical use, there is a problem that the apparatus for producing electrolyzed water can be provided only as remaining expensive.
Such electrolyzed acidic water or electrolyzed alkaline water is used in a wide range, for example, as drinking water and for washing of face, sterilization, cleaning and the like and from this respect, it may be desired to be delivered at a desired temperature in some cases.
However, the temperature of the electrolyzed water is risen relative to the temperature of subject water by the electrolysis and hence, it is necessary to cool the produced electrolyzed water again at the delivery time. In addition, the conductivity of the subject water is influenced by the temperature of the subject water and hence, even if the electrolyzed water is desired to be delivered as cold water, it may be desirable in respect of the electrolytic efficiency in some cases that the subject water is electrolyzed at a temperature higher than the temperature of the delivered water.
The prior art apparatus for producing electrolyzed water has no heating and cooling functions, and in order to adjust the temperature of the produced electrolyzed water or the subject water supplied, it is necessary to specially dispose a heater and/or a cooler in juxtaposition with the apparatus. In this case, the heater and the cooler are exclusively used and need to be designed and fabricated at each time in accordance with the specification of the apparatus for producing electrolyzed water.
On the other hand, it is known that at a pH value equal to or higher than 8, most of an aqueous solution of hypochlorous acid containing residual free chlorine is dissociated into hypochlorite ion OCl.sup.- to exhibit a significantly reduced sterilizing power, as compared with hypochlorous acid HClO, but at a pH value in a range of from 3 to 7, the aqueous solution of hypochlorous acid is maintained in the form of hypochlorous acid HClO to exhibit a drastically increased sterilizing power. An aqueous solution of hypochlorous acid having, for example, a pH value in a range of from 3 to 7, even if it has a concentration of residual chlorine therein as low as 30 to 60 ppm, provides a sterilizing effect equivalent to that of an aqueous solution of hypochlorous acid having a pH value of 8 and a residual chlorine concentration of 200 ppm. Thus, in providing such an equivalent sterilizing effect, the amount of chlorine added can be reduced, if the pH value is controlled appropriately.
There is a conventionally known method for producing sterilizing water of such a type, which comprises mixing water containing sodium chloride added therein with water containing chlorine added therein and subjecting a resulting mixture to an electrolysis in an electrolytic cell having no membrane, as described, for example, in Japanese Patent Application Laid-open No.237,478/93.
In this method, however, the concentration of residual chlorine can be controlled by adjusting the quantity of electricity and the amount of chlorine ion added, but if conditions for a producing apparatus such as the size of the electrolytic cell and the size and arrangement of electrode plates (particularly, a distance between the electrode plates) are determined, the quantity of electricity applied to subject water is fixed and from this respect, it is an only means to control the concentration of residual chlorine by adjusting the amount of chlorine ion added. For this reason, a given limit exists in the range of controlling the concentration of residual chlorine.
In addition, in this method, the contents of chlorine gas, hypochlorous acid and hypochlorite ion present in an aqueous solution of hypochlorous acid after electrolysis are controlled by the amount of chloric acid added to subject water. Therefore, this method is suitable for producing a solution having a large content of hypochlorous acid excellent in sterilizing effect, but in this method, it is difficult to produce, for example, weakly acidic sterilizing water having a pH value on the order of 7 to 8 and strongly acidic sterilizing water having a pH value on the order of 2.